1. Field of the Invention
The present invention relates to a semiconductor device and a manufacturing method thereof, and more particularly to a semiconductor device having a seal ring and a manufacturing method thereof.
2. Description of the Related Art
With recent improvements in the integration and performance of elements in semiconductor devices, demand has grown for further reductions in wiring thickness and wiring intervals. As miniaturization of the manufacturing process advances, wiring delays limit the operation speed. To deal with this problem, copper wire technology, in which low-resistance copper (Cu) or a copper alloy is used as wiring material, was proposed. It is difficult to process copper or a copper alloy by etching technology when the copper or alloy is used as wiring material. Therefore, a manufacturing method known as a Damascene method is typically employed.
In the Damascene method, a wiring trench is formed in an insulating film, a copper alloy thin film is deposited in the wiring trench, and then the copper alloy thin film is ground from the upper side thereof to leave only the part embedded in the wiring trench remaining. Thus, an embedded wire is formed. In the process for grinding the copper alloy thin film, a CMP (Chemical Mechanical Polishing) method is used.
To reduce the capacitance of the wiring when employing this type of copper wiring technology, a so-called low dielectric constant film is used as an insulating film instead of a conventional silicon oxide film. The low dielectric constant film has a dielectric constant (k) between approximately 4.2 and approximately 1.5.
This type of low dielectric constant film, particularly a porous film, has a low interface adhesion property as a mechanical characteristic (Modulus, Hardness). Therefore, during processes of the Damascene method in which stress is applied to the low dielectric constant film, such as the CMP process and a segmentation process, damage such as peeling may occur on the interface between the low dielectric constant film and an insulating film or another structure such as a seal ring that contacts the low dielectric constant film. As a result, the electric characteristic of the semiconductor device may be damaged.
Among semiconductor devices employing the Damascene method and a low dielectric constant film, a semiconductor device provided with a so-called seal ring that continuously surrounds an element region with the aim of preventing damage inflicted during dicing from reaching the element region is known, and a manufacturing method of such semiconductor device is also known (for example, Japanese Patent Application Kokai No. 2005-167198).
This conventional seal ring is capable of preventing cracks (peeling) that occur outside the element region during the segmentation process from spreading to the element region.